Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Nathaniel S. Rieger, Evan H. Stanton, Catherine A. MarlerDivision of labour allows group-living species to efficiently complete tasks while minimizing resource expenditure. This generally involves task allocation between individuals. In territorial defence and parental care specifically, division of labour can be completed using different strategies, often involving one or more individuals defending the territory while others care for offspring. Little is known, however, about division of labour by monogamous and biparental mammals. We investigated labour division strategies across territorial defence and pup retrievals by monogamous, biparental, territorial California mice along with the role of vocal communication in coordinating these behaviours. Male and female pair-bonded California mice display aggression towards same-sex intruders and retrieve pups while alone, but how pairs complete these tasks while together remains unknown. We found that California mouse pairs used one of two strategies during territorial defence: (1) joint defence or (2) divided defence. Overall, these strategies were not altered by the intruder sex or the birth of pups. However, postpartum individuals spent more time alone in the nest and pairs spent less time together investigating intruders. Pup retrievals, conversely, followed a sex-specific strategy where mothers retrieved pups in 89% of pairs while males retrieved pups in 11% of pairs. This study shows for the first time that a monogamous and biparental rodent uses different strategies to divide labour during vital tasks of territorial defence and pup retrieval. Moreover, we found that vocal communication via sustained vocalizations were predictive of aggressive behaviour but not retrieval behaviour, indicating that vocalizations may only play a role in coordinating specific behaviours. Importantly, these strategies were task dependent and robust across intruder sex and parental status, providing a framework for better understanding division of labour in mammals.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Anais Rivas-Torres, M. Olalla Lorenzo-Caballa, Rosa Ana Sánchez-Guillén, Adolfo Cordero-RiveraSperm quality and viability affect both male and female fitness. Most dragonfly and damselfly males translocate sperm from the testis to the seminal vesicle before each copulation, a behaviour known as intramale sperm translocation (ST). However, some published observations indicate that odonate males can occasionally skip ST prior to copulation. Our aim was to determine the circumstances under which males skip ST and how this might affect sperm viability. We allowed males of the damselfly Ischnura graellsii to perform ST (interrupting the copulation at this stage) and we studied ST behaviour during subsequent copulation. Males were randomly assigned to four treatments, which consisted of allowing the experimental male to copulate again 15 min or 1–3 days after his last ST. Fertility of females mated with the experimental males was analysed as a proxy for sperm viability. All males used the sperm that they translocated previously when the second mating took place 15 min after the manipulation, while the proportion of males that repeated ST increased steadily over time. Both treatment (time elapsed since last ST) and the interaction between treatment and ST (yes/no) had a significant effect on fertility, which decreased only in males that did not perform ST immediately before copulation. Additional experiments with damselflies of the genus Calopteryx showed also that males did not repeat ST when the time to the next copulation was less than a day. Our results suggest that sperm quality decays over time in odonates, and that males can choose whether to keep and reuse the sperm in the seminal vesicle or to discard it. We conclude that the special anatomical disposition of odonate males might increase selective pressures to maximize sperm viability and/or repeated intramale ST behaviour.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Devin R. de Zwaan, Sydney Barnes, Kathy MartinMelanin is a common pigment that can indicate individual quality to potential mates and social dominance to competitors. For many avian species, plumage melanism varies within both males and females. If predictive of individual quality, sexual selection may drive contrasting expressions of melanism for each sex, reflecting their different reproductive roles. For an alpine population of horned larks, Eremophila alpestris, we investigated whether plumage ornament size and darkness predicted morphometric traits, parental care and fitness correlates, and we evaluated support for assortative pairing. Males with darker crowns and larger masks were associated with greater wing length and mass, respectively. Males with darker ornaments were paired with females that provisioned nestlings at a higher rate, began nesting earlier in the season, had larger clutch sizes and ultimately had greater nest success. For females, plumage ornaments did not predict morphometric traits (i.e. wing length, mass), provisioning rate of the male partner, clutch initiation date or reproductive success. Instead, females with darker crowns provisioned nestlings more frequently and had larger clutches. Overall darker males tended to pair with darker females, but plumage ornament size did not correlate within mated pairs. We demonstrate that: (1) the darkness of plumage ornaments is a better predictor of fitness than ornament size and (2) darker males are associated with greater individual quality and reproductive investment of the female mate, while female darkness primarily predicts reproductive investment. These results indicate the potential for sex-specific selection pressures and mate choice based on the predictive value of plumage melanism.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Rebecca N. Carter, Cora A. Romanow, Sergio M. Pellis, Susan LingleAnimals ranging from mammals to fishes and even invertebrates play. Although this behaviour has been shown to improve the physical condition and survival of juveniles, we do not know exactly how these benefits are achieved. The motor training hypothesis suggests that play helps animals develop their motor skills. The self-handicapping hypothesis suggests that animals build cognitive and emotional skills to prepare for the unexpected, by using play as a way to practise losing and regaining postural control. We conducted focal observations and recorded videos of play to examine the specific form and timing of locomotor play in mule deer, Odocoileus hemionus, and white-tailed deer, Odocoileus virginianus, fawns, so as to test predictions associated with these two hypotheses. Consistent with the motor training hypothesis, play peaked early in life (≤3 weeks), which should coincide with development of the cerebellum and motor skills. These closely related species differ in antipredator tactics, so we predicted that they should display different motor patterns during play if it serves a motor training function. Although some characteristics reflected species-typical antipredator tactics (e.g. more ‘signal bounds’, leaps with long and high suspension, in white-tailed deer; more social play in mule deer), both species engaged in a similar amount of fast travel and similar rates of turns, traits that we expected to differ in line with their antipredator tactics. Consistent with the self-handicapping hypothesis, fawns of both species displayed high rates of nonfunctional manoeuvres, which were similar in form. However, these manoeuvres did not become more common as the fawns aged as expected if these help to develop the prefrontal cortex and cognitive skills. Our results suggest a refinement and blending of both hypotheses. Juveniles may play to develop similar motor skills rather than species-typical antipredator tactics, with nonfunctional manoeuvres to further promote the development of cognitive and motor skills during the early juvenile period.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Leanne A. Grieves, Mark A. Bernards, Elizabeth A. MacDougall-ShackletonChemical signalling is widespread across animal taxa. Even birds, once thought to have little or no sense of smell, are now known to possess a fully functional olfactory system and may thus respond to conspecific and heterospecific chemical signals. In birds, body odour derives primarily from preen oil, a complex chemical mixture that is potentially rich in information: for example, preen oil chemical composition differs between the sexes and among species. Hypothesizing that songbirds attend to preen oil odour cues in the contexts of intra- and interspecific communication, we presented breeding-condition adult song sparrows, Melospiza melodia, with preen oil odour cues in two-choice tests. We compared time spent in a Y-maze arm scented with preen oil from same-sex conspecifics relative to the absence of such odour; from opposite-sex relative to same-sex conspecifics; and from female brown-headed cowbirds, Molothrus ater (frequent brood parasites of song sparrows), relative to the absence of such odour. The time spent with same-sex conspecific preen oil was not significantly different than time spent without odour. However, both males and females spent more time with opposite-sex than same-sex preen oil. We found a sex-by-stimulus interaction with respect to female cowbird odour: male song sparrows spent more time with cowbird preen oil than without odour, but female song sparrows showed the opposite pattern. Our findings show that even relatively nonsocial species can attend to the information contained in preen oil secretions.

Abstract: Publication date: Available online 4 September 2019Source: Animal BehaviourAuthor(s): Davide Baldan, Teja Curk, Camilla A. Hinde, Catherine M. LessellsIn species with biparental care, the amount of care devoted to offspring is affected by the negotiation rules that the parents adopt. Recently, turn taking in provisioning visits has been proposed as a negotiation rule by which parents respond to their partner's behaviour, which results in a perfect alternation of the nest visits by the parents. Empirical evidence suggests that parents do not strictly alternate their visits, and, so far, this imperfect alternation has received no experimental investigation. In this study, we tested whether alternation of nest visits might be subject to time constraints affecting the ability of parents to strictly take turns. We manipulated the workload of 15 great tit, Parus major, pairs using a short-term brood size manipulation. Parental nest visits alternated more in reduced than control and enlarged broods. To understand whether this variability could be caused by changes in turn taking, we explored the rate and regularity of the parents' intervisit intervals. Treatment differences in alternation were still present when controlling for the rate and regularity of the visits by each of the two parents, suggesting that workload also affected alternation via the temporal sequence of the intervals (e.g. via turn taking). Our results show that alternation of nest visits varies in response to workload and is not merely a by-product of variation in visit rate or regularity.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Md Kawsar Khan, Marie E. HerbersteinSexually dimorphic traits in males are thought to evolve via female preference or male–male competition. Alternatively, in species without overt male displays or female mate choice, dimorphic coloration may function as a warning signal to conspecific males thereby avoiding costly harassment. We aimed to determine the function of sexual dimorphic coloration in the damselfly Xanthagrion erythroneurum in which males, but not females, have conspicuous blue bands on the tip of the abdomen. We show that the male blue bands and female black abdomen are chromatically and achromatically discriminable against their natural background. Moreover, the male blue bands and their adjacent abdominal segments generate higher internal contrast than female abdominal segments. We conducted two sets of experiments to test alternative hypotheses that the male blue bands are (1) the target of female mate choice, or (2) an intrasexual aposematic signal to avoid male mating harassment. We hid male blue bands by painting them black and measured female preference between the manipulated and the nonmanipulated (control) males. We found no difference in mating success between the control and manipulated males, thereby rejecting the female preference hypothesis. To test whether the blue bands function as a warning signal, we manipulated the females by painting male-like blue bands on their abdomen and measured the male response to those females relative to control females. Females with artificial blue bands on the terminal abdomen were mated less frequently than control females. However, when we painted blue bands on the anterior abdominal segments, the males did not discriminate between control and painted females. Our study demonstrates that dimorphic coloration advertises the males' unprofitability as mates to conspecifics thereby reducing intrasexual harassment.

Abstract: Publication date: Available online 31 August 2019Source: Animal BehaviourAuthor(s): Davide Baldan, Matteo GriggioRaising a family is not free of conflict for parents, as each parent benefits when its partner provides more care for the offspring. Resolving this conflict requires cooperation between the parents. One way to achieve such cooperation might be to coordinate parental provisioning by synchronizing (i.e. returning to the nest at the same time) or alternating (i.e. taking turns) offspring provisioning at the nest. Empirical studies in birds indicate that pair coordination of the nest visits is common; however, it is unknown whether this behaviour is directly related to different outcomes of sexual conflict, such as brood desertion. We used the rock sparrow, Petronia petronia, a species with high levels of sexual conflict, to explore whether alternation and synchrony of the nest visits were related to later brood desertion. Pairs with no desertion alternated and synchronized their nest visits more than pairs in which one sex deserted. This difference in coordination was not simply a by-product of differences in provisioning by the parents. Synchrony of the visits also increased with offspring age in the pairs with no desertion. We provide evidence, for the first time to our knowledge, that the degree of parental coordination is strongly associated with the ultimate consequence of sexual conflict, brood desertion, supporting the idea that coordination in parental behaviour might promote conflict resolution.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): Pietro Pollo, Danilo G. Muniz, Eduardo S.A. SantosMale preference for high-quality females is expected to evolve when male reproductive potential is restricted. However, when there is competition among males, some models predict the evolution of assortative male mate choice, in which good competitors choose high-quality females while poor competitors choose lower quality females to avoid competition. In Trichonephila clavipes spiders, males have limited sperm supply and fight for access to females. We tested whether female quality and male size (a proxy of fighting ability) influence male decisions in T. clavipes. We used field experiments in which males could choose between two available females in a scenario free of competition. We found that males choose their mates based on both female size and female recent pairing status (whether the female was accompanied by a male before the experiment). Importantly, male mate choice was plastic, and varied with male size, as large males preferred larger females that were recently unpaired, medium-sized males showed no preference and small males preferred smaller, recently paired females. Because all females appear to attract males, we predict that variation in male mate choice attenuates sexual selection on females. Our findings confirm the prediction of variable male mate choice when there is male–male competition and male reproductive potential is restricted, a pattern that may be common, but hard to detect.

Abstract: Publication date: October 2019Source: Animal Behaviour, Volume 156Author(s): S. Nicola Jung, Silke Künzel, Jacob EngelmannNavigation is a ubiquitous challenge to mobile animals as it is essential for finding mates, food and shelter. It can rely on self-generated (idiothetic) as well as external (allothetic) information. The contribution of either source of information depends on multiple factors, including the sensory modality. Far-range modalities such as vision have frequently been studied in the context of navigation, but the extent to which near-range sensory systems provide information for navigation is much less understood. Here we focused on spatial learning in the weakly electric fish Gnathonemus petersii. During their nocturnal excursions these fish typically rely on their short-range active electric sense to explore their environment. We addressed how these fish navigate and how electrosensory information is integrated in navigation. All fish learned to localize a target in a Barnes-like maze. In a series of transfer tests, we found that fish followed an idiothetic navigation strategy. When this strategy failed, fish were able to integrate electrosensory information to complete the task. Our results indicate that the active electric sense contributes to navigation in a resource-efficient and context-dependent manner. Together they show that weakly electric fish can incorporate highly localized sensory input in egocentric navigation. Extending these results will be important to reveal the sensory mechanisms of egocentric navigation in fish as well as to research whether and how spatially confined near-range sensory information might be used to form global representations of space.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Amanda M. Adams, Amber Patricio, Roja Manohar, Michael SmothermanHow bats mitigate mutual interference is a long-standing question that has ecological and technological implications as biosonar systems continue to outperform artificial sonar systems in noisy, cluttered environments. Echolocating bats display a mutual suppression response, slowing their pulse emission rates when flying in groups to gain a net improvement in sonar performance. However, flight paths, directional effects, plus contextual and attentional processes influence the levels of mutual interference, causing some noises to be more deleterious than others. To tease apart the impact of these factors, we used playback experiments with flying Mexican free-tailed bats, Tadarida brasiliensis, to test whether the relative directional orientation of an interfering signal versus its returning echoes had a greater impact on a bat's sonar performance. We tested two competing hypotheses: (1) the intensity hypothesis predicts that a signal that is emitted towards a signalling bat is louder and will mask returning echoes more than a signal that is emitted in the same direction as a bat's emitted signal; (2) the similarity hypothesis predicts that a signal that is emitted in the same direction as a bat's signal will create echoes similar in amplitude and timing to those of the signalling bat's own echoes , which should cause greater interference than a loud, less similar signal. We analysed emission rates of bats navigating in both open and cluttered spaces while we varied the directional orientation of an artificial stimulus relative to the bat's flight trajectory. Both emission rates and navigational performance decreased significantly when playback was directed in the same heading as the flying bat, indicating that competing echo wave-fronts are more disruptive to a flying bat than the much louder source signal that produced them. This observation is important because it potentially reveals the impact of attentional processes on sonar performance. This study provides new information on how echolocating bats experience interference and the behavioural strategies they use to overcome jamming.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Scott K. Sakaluk, Jeannine Oldzej, Christine J. Poppe, Jenny L. Harper, Ian G. Rines, Kylie J. Hampton, Kristin R. Duffield, John Hunt, Ben M. SaddAlthough inbreeding depression in life-history traits has been well characterized, inbreeding effects on mating behaviour and sexually selected traits have been less well studied. Here, we assess levels of inbreeding depression in a number of fitness-related reproductive parameters of female decorated crickets, Gryllodes sigillatus. We predicted that due to direct negative effects of inbreeding and a potential trade-off between reproduction and current survival, as suggested by effects of inbreeding on immunity, inbred females would show significantly reduced reproductive output compared with outbred females. We also examined sex-specific effects of inbreeding on mating competency, focusing specifically on the female's decision to mount a male and the male's ability to transfer a spermatophore. We predicted that any inbreeding depression in sexual competency should be more evident in the success of spermatophore transfer than in female mounting propensity because of the tighter link between mating success and fitness in males than in females. Inbred females produced fewer offspring with longer development times compared with outbred females, results consistent with theory, as inbreeding depression is expected to be more severe for traits more tightly coupled with fitness. Inbreeding also had sex-specific effects on sexual competency. Inbred females were less likely to mount outbred males than were outbred females to mount inbred males. Inbred males were significantly less likely than outbred males to transfer a spermatophore regardless of female inbreeding status. These results reveal that inbreeding may have unexpected consequences for sexual competency and highlight the importance of considering mating behaviour when assessing effects of inbreeding within populations.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Federica Amici, Anja Widdig, Julia Lehmann, Bonaventura MajoloThe ability to innovate and the social transmission of innovations have played a central role in human evolution. However, innovation is also crucial for other animals, by allowing them to cope with novel socioecological challenges. Although innovation plays such a central role in animals’ lives, we still do not know the conditions required for innovative behaviour to emerge. Here, we focused on interindividual differences in innovation by (1) extensively reviewing existing literature on innovative behaviour in animals and (2) quantitatively testing the different evolutionary hypotheses that have been proposed to explain interindividual variation in innovation propensity during foraging tasks. We ran a series of phylogenetically controlled mixed-effects meta-regression models to determine which hypotheses (if any) are supported by currently available empirical studies. Our analyses show that innovation is more common in individuals that are older and belong to the larger sex, but also in more neophilic and/or explorative individuals. Moreover, these effects change depending on the study setting (i.e. wild versus captive). Our results provide no clear support to the excess of energy or the bad competitor hypotheses and suggest that study setting and interindividual differences in traits related to personality are also important predictors of innovation.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Leonardo Palloni Accetti Resende, Vitor Passos Rios, Hilton F. JapyassúFor social life to emerge, the benefits of group living must overcome its costs, a balance that depends on the life history of the organisms and may occur more easily in some taxa than in others. Among spiders, sociality is uncommon. Social species evolved several times independently through the subsocial route, a process connected to a mean reduction in the aggressiveness and boldness of the individuals, with a simultaneous increase in the variability of personality. Personality variability is at the root of spider's division of labour, but the mechanism for its increase is yet poorly studied. One possible mechanism for the evolution of the variability in personality would be the creation of a new selective regime by the newly evolved, larger colonial webs, which could offer a mix of more protected and predator-exposed areas. To evaluate this hypothesis, we present an ecological-evolutionary model in which heterogeneous, spatially explicit variation in predatory selective pressures appear through changes in niche construction. Our model shows that social webs, by providing areas of greater protection against predators, increase the survival of the shyest variants, leading to increased intracolonial variability in personality. We speculate that this greater protection allowed social species the possibility of colonizing otherwise inhospitable environments, and that larger intracolonial personality variance, associated with social web spatial heterogeneity provided the basis for social organization through division of tasks among colony members.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Tyrone Lucon-Xiccato, Angelo Bisazza, Andrea PilastroMany animals, from humans to invertebrates, exhibit sexual preference for unfamiliar partners. This may reduce the risk of inbreeding and increase offspring heterozygosity. An alternative less tested hypothesis is that selection for neophilia in other contexts (e.g. exploration of unfamiliar environments) may promote mate preference for unfamiliar partners. We tested whether exploratory tendency covaries with female preference for unfamiliar mates in the guppy, Poecilia reticulata, a species in which exploratory behaviour show significant phenotypic and genetic variation. We measured the exploratory behaviour of females using an unfamiliar environment test. The same females were also tested for preference for an unfamiliar male over a male with which they had spent the previous 24 h. We found that a female's tendency to explore an unfamiliar environment was positively correlated with the strength of her preference for unfamiliar males. Our results support the hypothesis that exploration might play a role in the evolution and maintenance of preference for unfamiliar males via functional pleiotropy.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): David N. Fisher, Rolando Rodríguez-Muñoz, Tom TregenzaReproductive success is often highly skewed in animal populations. Yet the processes leading to this are not always clear. Similarly, connections in animal social networks are often nonrandomly distributed, with some individuals with many connections and others with few, yet whether there are simple explanations for this pattern has not been determined. Numerous social interactions involve dyads embedded within a wider network. As a result, it may be possible to model which individuals accumulate social interactions through a more general understanding of the social network's structure, and how this structure changes over time. We analysed fighting and mating interactions across the breeding season in a population of wild field crickets under surveillance from a network of video cameras. We fitted stochastic actor-oriented models to determine the dynamic process by which networks of cricket fighting and mating interactions form, and how they co-influence each other. We found crickets tended to fight those in close spatial proximity to them and those possessing a mutual connection in the fighting network, and heavier crickets fought more often. We also found that crickets that mated with many others tended to fight less in the following time period. This demonstrates that a mixture of spatial constraints, characteristics of individuals and characteristics of the immediate social environment are key for determining social interactions. The mating interaction network required very few parameters to understand its growth and thus its structure; only homophily by mating success was required to simulate the skew of mating interactions seen in this population. This demonstrates that relatively simple, but dynamic, processes can give highly skewed distributions of mating success.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Clare McArthur, Patrick B. Finnerty, Melissa H. Schmitt, Adam Shuttleworth, Adrian M. ShraderTo forage nonrandomly, animals must discriminate among food items. Foods differ in look, smell and taste, providing cues for foragers with appropriate senses. Irrespective of the sensory modality, however, foragers can only use cues effectively if they can detect sensory signals above background noise. Recent evidence shows that foraging mammalian herbivores can detect plant odours, but their capacity to select preferred plants in a noisy olfactory background is unknown. Using choice trials, we tested whether the African elephant, Loxodonta africana, uses plant odour as a salient cue despite increasingly complex and challenging background odours. We first established their preference for familiar plant species. We then tested their capacity to discriminate and select preferred plants based on odour alone. We found that elephants successfully chose preferred species even when presented with complex background odours from nonpreferred plants mimicking multispecies vegetation patches. Elephants also succeeded despite our attempt to mask distinguishing odours with large amounts of a synthetic green leaf volatile. GC–MS analysis confirmed that volatile organic compound profiles differed between plant species. In demonstrating that elephants exploit plant odours even when the signal from preferred plants is embedded in sensory noise of background odours, we provide crucial behavioural evidence that olfaction provides an efficient mechanism for selective, nonrandom foraging. Whether mammalian herbivores recognize novel odours, for example from newly invading plant species, or when air pollution degrades odours of familiar plants, needs investigating. Accounting for the capacity of mammalian herbivores to use plant odour cues will improve models of both their foraging behaviour and the ecosystem impacts of their foraging.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Maria Santacà, Melania Busatta, Tyrone Lucon-Xiccato, Angelo BisazzaAnimal species differ considerably in their ability to detour around a see-through obstacle to reach a goal positioned behind it. This variation is commonly assumed to derive from interspecific differences in the cognitive functions involved in the execution of the task, such as spatial abilities and inhibitory motor control. A teleost fish, the guppy, Poecilia reticulata, has recently been found to outperform many mammals and birds in this type of task. To determine whether this is a typical condition in teleost fish or whether detour abilities vary among fish species as observed in mammals and birds, we compared four distantly related teleosts in a transparent barrier task using a group of conspecifics as the goal. The scores of three species (Poecilia reticulata, Xenotoca eiseni, Oryzias sarasinorum) were similar to those previously reported for fish. The remaining species, the zebrafish, Danio rerio, showed a much higher performance, close to that of warm-blooded animals with the highest scores (e.g. corvids and monkeys). In comparative cognition studies, contextual variables rather than differences in cognitive ability may be responsible for observed differences between species. In a second experiment, we found that the four species were similarly gregarious, excluding a different motivation to reach the target as an explanation for the different performance. In another experiment, however, we found evidence that the zebrafish's higher detour performance might be due to a sensory advantage. Zebrafish used olfactory cues (towards which the barrier was opaque) to navigate to the social stimuli, whereas the guppy, which we used as a control species, preferentially relied on visual information. This study highlights the importance of sensory differences as a source of potential experimental confound in comparative cognition research.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Ramy Ayoub, Eric Armstrong, Noam Y. MillerThe costs and benefits that come from being part of a group have most often been categorized by their adaptive function, such as reducing predation risk or increasing foraging competition. However, collective behaviours may also be characterized by several different behavioural mechanisms. For example, individuals may have a relatively fixed attraction to any group, as well as being able to flexibly use the information they derive from observing the group to make choices. We label these two mechanisms ‘fixed’ and ‘informational’. In most situations, both mechanisms encourage group cohesion. Here, we placed fixed and informational mechanisms in conflict by training zebrafish, Danio rerio, to move away from or ignore a conspecific group in order to find food. Fish failed to learn the task when the group was visible to them while making their choice, but they were able to learn the task when the group was visually obscured. Fish trained to approach the group to find food were able to learn to do so under both conditions. Our results suggest that fish exhibit a prepotent group-joining response, even when this is potentially maladaptive – a type of conformity. This response can be inhibited under certain conditions, such as when the group is not immediately visible.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Alicja Laska, Brian G. Rector, Anna Skoracka, Lechosław KuczyńskiDispersal involves many behavioural interactions that if inefficient or ineffectual would lead to serious fitness consequences. Such costs would be particularly dear for passively dispersing organisms for which direction of movement is determined by external forces. In this study, we investigated whether environment and morphology influence dispersal behaviours of a passive, aerially dispersing organism, the eriophyoid wheat curl mite, Aceria tosichella. We used a wind tunnel to generate stable wind speeds and analysed mite behaviour, morphology and dispersal rate for each wind speed treatment. We found that dispersal events were phenotype and context dependent with an important behavioural component. Aerial dispersal increased significantly via chains formed by individuals and mites dispersing in chains were significantly more elongated than controls. This difference in shape interacted significantly with wind speed but diminished at high wind speeds. Contrary to expectations, we found that an upright position was not related to the likelihood of being blown away. The results indicate that departure events for this mite are influenced by the interaction of behaviour, morphology and environment. Our study represents a substantial step toward explaining wheat curl mite dispersal and its colonization potential, with implications for passively dispersing organisms in general.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Michal Šulc, Jolyon Troscianko, Gabriela Štětková, Anna E. Hughes, Václav Jelínek, Miroslav Capek, Marcel HonzaOne of the most effective defensive strategies of hosts against brood parasites is rejection, commonly achieved by ejection of the parasitic egg or desertion of the parasitized nest. Nest desertion should be a costlier strategy than egg ejection, because birds must thesn spend additional time and energy renesting, and therefore we still cannot explain why some individuals desert their nests rather than eject parasitic eggs and continue a given breeding attempt. The great reed warbler, Acrocephalus arundinaceus, is a frequent host of the common cuckoo, Cuculus canorus, and is known to use both types of rejection response. By measuring cuckoo egg mimicry, we investigated the hypothesis that the hosts desert if they cannot reliably recognize the cuckoo egg in their nest. We predicted that we would find better mimicry when hosts deserted rather than ejected. However, we did not find a difference in mimicry between these two groups of nests, implying that host females do not desert because they cannot reliably recognize the parasitic egg. We also showed that neither the date in the season nor the age of the host females influenced the type of rejection. Other factors potentially eliciting nest desertion, including host personality, host, inability to eject, excessive clutch reduction and visibility of the cuckoo female at the host nest, are discussed. Finally, we suggest that desertion may persist as a host defensive strategy against brood parasitism because it is not as costly as previously assumed and/or it is beneficial for host females in good physical condition.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Peter Santema, Mihai Valcu, Michael Clinchy, Liana Y. Zanette, Bart KempenaersAn increase in the perceived risk of predation triggers many behavioural changes in prey species, which can have consequences for their reproductive success. Perceived predation risk may also influence investment in extrapair activities and, as a result, the frequency of extrapair paternity (EPP), but this possibility remains largely untested. Here we report on a study of a small passerine bird, the blue tit, Cyanistes caeruleus, in which we experimentally manipulated perceived predation risk by intermittently broadcasting predator calls throughout the breeding season. We found no evidence that the treatment affected two behavioural indices of extrapair activity (extrabox visits and the time of emergence from the nestbox in the morning during the fertile period) or the rate of EPP itself. The treatment also had no significant effect on clutch size, hatching success or most reproductive behaviours. However, nests in the predator playback treatment produced more fledglings, which was mainly due to a lower frequency of complete brood mortality. We discuss potential explanations for this finding, as well as for the lack of evidence for other effects of the predator playback treatment on blue tit reproductive behaviour. Several measures of reproductive performance suggest that the year in which the experiment took place was an unusually poor one and further work is therefore needed to assess the generality of our findings.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Samuel R. Matchette, Innes C. Cuthill, Nicholas E. Scott-SamuelPrey and ambush predators that rely on concealment face a major constraint: motion breaks their camouflage. However, dappled light is a common feature of sunny, vegetated habitats and can, when conditions are windy, become a source of dynamic visual noise. We tested the idea that this could mask movement, reducing the risk of detection. Newly hatched domestic fowl chicks, Gallus gallus domesticus, a proxy for wild forest-floor birds, were trained to peck moving, on-screen prey presented among two sources of dynamic dappled light: computer-simulated and that created with a mirror ball. Dynamic dapple, however produced, increased the chick's latency to both fixate and peck the prey. Furthermore, we show that dynamic visual noise masks motion in a way that static visual noise does not. This reduction in foraging efficiency should, we predict, have significant consequences for an organism's choice of habitat (as prey), foraging area (as predator) and its pattern of movement within a habitat.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Emily J. Williams, W. Alice BoyleUnderstanding the causes and consequences of dispersal is key to identifying selective pressures underlying species-level variation in biogeography, metapopulation dynamics and adaptive capacity. We tested the hypotheses that nest predation and/or brood parasitism avoidance drive breeding dispersal decisions and that dispersal functions to reduce subsequent reproductive failure in grasshopper sparrows, Ammodramus savannarum, breeding in eastern Kansas, U.S.A. Over 2 years, we monitored the fate of 222 nests and the movements of 144 parents. We established the spatiotemporal patterns of nest success among all nests, then related nest predation and parasitism to subsequent dispersal behaviour and reproductive success. Birds were more likely to disperse following nest predation, but decisions were unaffected by parasitism. Dispersers experienced higher chances of subsequent nest survival than did site-faithful individuals. Although second nests were parasitized less often than were first nests, dispersers did not experience substantially lower parasitism than did site-faithful individuals, suggesting that the challenges of predation and brood parasitism may be solved in different ways. This study represents one of few tests of alternative hypotheses explaining dispersal decisions of songbirds within seasons and represents a rare case study of the consequences of breeding dispersal on subsequent reproductive success. Our results suggest that differences in dispersal tendencies may result from variation in risk-response thresholds rather than alternative causal drivers.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Shivani Krishna, Tamar KeasarForaging bees expend considerable time and energy handling flowers that are morphologically complex (with concealed food rewards) while simple flowers (with readily available rewards) bloom simultaneously in their foraging environment. Previous studies have investigated the consequences of floral morphology for both foragers and plants, often treating ‘complex’ and ‘simple’ morphologies as dichotomous traits. How pollinators' foraging choices and success vary along a floral complexity gradient has received less attention. Here we investigated, using real flowers of increasing morphological complexity, how complex flowers are chosen and handled by naïve and experienced bumblebees when presented along with simple ones. Intact flowers of Tecoma x ‘Orange Jubilee’ (Bignoniaceae), Antirrhinum majus (Plantaginaceae) and Lupinus pilosus (Fabaceae) represented a gradient of increasing morphological complexity. We manipulated some flowers of each species to look simple with a readily accessible food reward, while keeping their colour and odour unchanged. Bombus terrestris workers were given four simple and four complex flowers of a single species with equal rewards in choice assays in a flight room. Sixty per cent of naïve foragers chose a complex flower on their first visit to all three flower species arrays. Experienced bees visited complex flower types of all three species but had lower feeding success and longer handling times on the more complex species. Thus, the bees' foraging efficiency on the complex option decreased with increasing complexity of the flowers, while individual variation in feeding success on the complex option was increased. These results suggest that inexperienced foragers and unsuccessful feeding attempts increasingly contribute to floral pollination along the morphological complexity gradient.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Adam R. Reddon, Cody J. Dey, Sigal BalshineActing submissively may inhibit aggression and facilitate the termination of contests without further escalation. The need to minimize conflict is vital in highly social species where within-group interactions are frequent, and aggression can dampen group productivity. Within social groups, individual group members may modulate their use of submissive signals depending on their phenotype, the value of the contested resource, their relationship to the receiver of the signal and the characteristics of the local environment. We predicted that submissive behaviour would be more common when signallers had limited ability to flee from conflict, when signallers were of a low rank within the group, when signallers and receivers differed substantially in body size (and thus in fighting ability), and when signallers and receivers were of opposite sex and therefore not directly in competition over reproductive opportunities. We tested these predictions using social network analyses on detailed behavioural observations from 27 social groups of the cooperatively breeding cichlid fish Neolamprologus pulcher. Congruent with our prediction, submissive behaviour was more common when there were fewer shelters available, suggesting that constraints on fleeing behaviour may increase the use of submission. Also fitting with predictions, submissive behaviour was more common with increasing body size asymmetry between the competitors, among lower ranked fish and in interactions between opposite-sex dyads, which supports the idea that signalling submission is adaptive in contests over low-value resources. Our findings suggest that subordinate N. pulcher are primarily concerned with being tolerated within the social group and may use submissive behaviour to avoid escalated conflict. Our findings offer a window into the factors that influence signals of submission in a highly social vertebrate.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Daniel J. Mennill, Stéphanie M. Doucet, Amy E.M. Newman, Heather Williams, Ines G. Moran, Ian P. Thomas, Bradley K. Woodworth, Mikayla M.K. Bornais, D. Ryan NorrisAnimals often live within close proximity of multiple conspecific individuals, allowing them to eavesdrop on other animals' signalling interactions to guide their own social behaviours. For a young animal that is learning to vocalize, eavesdropping on vocal interactions between adults may provide a rich source of information: young animals might preferentially learn vocalizations that are commonly heard in interactions between adults or that are heard to be effective for attracting mates or defending resources. We used a multispeaker playback experiment with wild Savannah sparrows, Passerculus sandwichensis, to test the hypothesis that vocal learning is guided by eavesdropping. Over a 6-year period, we tutored young Savannah sparrows with experimental tutor songs; half of the tutor songs were broadcast in simulated vocal interactions between two tutors, and the other half were broadcast as noninteractive, stand-alone solo performances. If eavesdropping plays an important role in guiding vocal learning, we predicted that young birds would preferentially learn the vocalizations heard during interactions between tutors. In contrast to our prediction, young Savannah sparrows did not preferentially learn interactive tutor songs; birds were similarly likely to learn songs heard in an interactive context (N = 13) and in a noninteractive context (N = 17). Analysis of live adult tutors' reactions to the loudspeakers showed that they responded with similar vocal behaviour during interactive and noninteractive treatments, and therefore their vocal behaviour did not compromise the playback simulation. We conclude that eavesdropping on vocal interactions between tutors does not appear to be essential for vocal learning of wild Savannah sparrows.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Sheila Marie Holmes, Edward E. Louis, Steig Eric JohnsonInterspecific competition can strongly influence patterns of space use in animal communities, particularly between closely related species, and may be exacerbated in marginal habitat. This may be important in Madagascar, as lemurs face diminishing resources due to deforestation. We examined the range overlap and spatiotemporal relationships of three species of frugivorous lemur in the fragmented forests of Kianjavato, Madagascar. We conducted simultaneous location and behaviour sampling of black-and-white ruffed lemurs, Varecia variegata, red-fronted lemurs, Eulemur rufifrons, and red-bellied lemurs, Eulemur rubriventer, at two sites over a period of 11 months. We used Doncaster's index of dynamic interaction to investigate the relative amount of time species spent within 30 m and 100 m of each other, compared to the time expected based on random use of location points. All three species showed low core range overlap compared to home range overlap, and while core overlap was higher between interspecific groups than intraspecific groups, the difference was not substantial. Conversely, no spatiotemporal avoidance was observed, and red-fronted lemurs showed positive association (indicating possible attraction) with both red-bellied and ruffed lemurs. These positive spatiotemporal associations may be related to shared resource use in small forests, or predation avoidance strategies. At present, these species may rely more on spatial segregation and niche separation than spatiotemporal avoidance to minimize interspecific competition.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Madeleine M. Ostwald, Zachary Shaffer, Stephen C. Pratt, Jennifer H. FewellThe advantages of group living are partially offset by the cognitive challenges associated with maintaining social boundaries. These challenges can give rise to recognition mechanisms that adaptively integrate information across multiple sensory modalities. The valley carpenter bee, Xylocopa varipuncta, nests in dead wood in large aggregations of up to several dozen nests. This study investigates the proximate mechanisms by which returning foragers quickly and reliably identify their own nest entrance within a high-density nesting site. We manipulated long- and short-range visual cues associated with nest entrances, removed chemical cues on the inside of nest entrances and added chemical cues from foreign conspecific bees. By measuring the effect of these manipulations on nest search time and search accuracy, we assessed the importance of visual and olfactory sensory modalities in allowing carpenter bees to locate their nests within aggregations. Our results support the hypothesis that both visual and olfactory cues can facilitate nest localization. Removal of nest olfactory cues did not significantly disrupt homing, suggesting that olfactory information may not be necessary for nest localization when visual information is available. However, the addition of olfactory cues from unfamiliar conspecific bees actually aided nest localization rather than disrupting it, suggesting that bees may use generalized species odour cues for homing. Due to intense nest site competition within aggregations, nest localization may have important social implications for maintenance of high-density nesting.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Anja Ebenau, Christoph von Borell, Lars Penke, Julia Ostner, Oliver SchülkeAnimal social bonds are defined as stable, equitable and strong affiliative and cooperative relationships similar to human friendships. Just as with human friendships, social bonds are thought to function as alliances that generate adaptive benefits via support in critical situations. In humans, similarity in many sociodemographic, behavioural and intrapersonal characteristics leads to trust and is predictive of friendships. Specifically, personality homophily (that is, the tendency of individuals to form social bonds with others who have a similar personality) may increase predictability and facilitate trust and reciprocity between partners with compatible behavioural tendencies. While evidence for social bonding in animals is accumulating, far less is known about its predictors. Here, personality homophily effects on the formation and maintenance of social bonds are shown in 24 wild male Assamese macaques at Phu Khieo Wildlife Sanctuary, Thailand. Dyadic bond strength increased with increased similarity in the trait Gregariousness (i.e. frequent and diverse neighbours within 5 m and pronounced social tolerance, as shown by high rates of friendly approaches to and by others). To differentiate whether homophily indeed predicted bond formation or whether bonded males’ personalities became more similar over time, we tested the stability of the Gregariousness traits in a subset of immigrating males that had to form new bonds. Gregariousness in these males remained stable, suggesting that males do not adapt their personality to their partner. Our results support the idea of a shared evolutionary origin of homophily as a partner choice strategy in human and nonhuman animals. The main selective advantage of personality similarity in animal social bonds may result from a more reliable cooperation between individuals with similar cooperative behavioural tendencies.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Anshuman Swain, William F. FaganAnimals tend to learn and make decisions inductively, and simple, individual-level behavioural decisions can scale up to yield interesting emergent properties at the population level. The minority game is a theoretical formulation based on the principle of inductive learning, wherein a group of individuals, each facing two equivalent choices, self-organize to achieve maximum coordination. Coordination increases with memory length up to a certain threshold, and thereafter, at very high memory lengths, decisions resemble a random choice game. We invoked and observed minority games in guppies, Poecilia reticulata, by forcing them to choose between two symmetric chambers in a series of repeated trials. At an intermediate timescale, guppies self-organized into a globally efficient state featuring maximum coordination. After a large number of trials, the guppies approached a steady state in which they behaved as if they were randomly choosing between the two chambers. Intriguingly, both the time taken to reach this globally efficient state (i.e. learning time) and the grouping behaviour for decision making depended on the sexual composition of the fish populations. We identified a positive correlation between group size and learning time in the experiments, which we further explored using simulations to uncover the form of decision-making framework at play, testing between a leader-based framework and a consensus-based one. Our simulations supported the presence of a consensus-based decision-making process in the system. This work also provides an unexplored general framework to further investigate and understand simple decision-making dynamics and structure in animal groups.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Andrew P. Anderson, Adam G. JonesWithin Syngnathidae (pipefish, seadragons and seahorses), male pregnancy often results in choosy males and competitive females. Females in these species often evolve secondary sexual traits and engage in courtship displays that make their ornaments more noticeable to males. Most syngnathids probably continue to grow larger throughout their lives, but we know little about the relationship between age and mating competition in these taxa. Here, we use the Gulf pipefish, Syngnathus scovelli, to investigate the roles of ornament size, courtship activity level, age and fecundity in female mating competition. We conducted male choice trials that allowed males to choose between similarly sized females of different ages. We also measured age and size at maturity. We found that females with larger ornaments were deeper bodied and engaged in longer courtship displays, yet males chose females based on body depth and display rather than ornamentation. This result suggests that ornamentation serves to help males assess female quality. Female age plays no role in male choice or in female ornamentation. Our finding that males care more about female phenotype than female age considerably simplifies the interpretation of mating patterns in natural populations of Gulf pipefish, which are characterized by considerable age structure.

Abstract: Publication date: September 2019Source: Animal Behaviour, Volume 155Author(s): Xianfeng Yi, Yueqin Yang, Mingming ZhangThe rapid sequestering hypothesis predicts that scatter-hoarding animals quickly sequester food items by storing seeds in caches near seed sources to reduce competition. However, tests of this hypothesis usually use food-hoarding animals with a single load or a small load size. How multiple-load animals place their caches between food sources and nests remains largely unknown. Here, we hypothesized that multiple-load animals, compared to single-load animals, may not necessarily sequester food items but adopt alternative hoarding strategies due to their multiple-load ability. In this study, we presented seeds at different distances from the nests of the multiple-loading Siberian chipmunk, Tamias sibiricus, and mapped the spatial distribution of their caches in multiple-compartment enclosures to test our hypothesis that a multiple-prey loader will consistently establish caches near nests rather than rapidly sequester near the seed source. By using multiple-compartment enclosures with different distances between the seed source and nests, and given potential intra- and interspecific competition, we found chipmunks consistently placed their caches near nests but away from the seed source. Cache placement near nests may serve as an alternative strategy that not only guarantees a maximum harvest rate at the seed source but also ensures effective cache defence near nests. Moreover, scatter-hoarding seeds near nests may alternatively guarantee a food supply if larder-hoarded seeds are depleted or lost. Unlike seeds sequestered near food sources, caches near nests imply long dispersal distances for seeds in our study. Therefore, scatter hoarding by multiple-prey loaders is expected to be ecologically important for the structure and function of tree communities, especially in ecosystems in which seeds depend on food-hoarding animals for dispersal and germination.

Abstract: Publication date: Available online 19 July 2019Source: Animal BehaviourAuthor(s): Susan A. Foster, John A. BakerBehavioural phenotypes are notable for their plasticity, in that individual behaviour patterns can be expressed ephemerally in response to an appropriate stimulus and then disappear. In the absence of an appropriate stimulus, behavioural phenotypes can remain unexpressed over many generations, yet the capacity to perform the behaviour can be retained. Here we discuss potential evolutionary influences of unexpressed behavioural phenotypes using two examples, one from the post-glacial adaptive radiation of the threespine stickleback fish, Gasterosteus aculeatus, and one from a far more ancient radiation, that of Pheidole ants. These radiations demonstrate that unexpressed phenotypes can persist for thousands or more generations in a condition that permits re-expression when an appropriate stimulus appears in the environment. We describe possible explanations for persistence of unexpressed phenotypes and demonstrate that in the absence of an appropriate phylogeny, re-expressed traits could be interpreted as true novelties in the group. We then discuss the way in which loss of expression can lead to parallelism in adaptive radiations — a mechanism that is rarely considered. We conclude by examining the way in which reappearance of unexpressed ancestral traits has the potential to facilitate population persistence if ancestral environments reappear and discuss the reasons that the evolutionary implications of behavioural plasticity are not better studied.

Abstract: Publication date: Available online 16 July 2019Source: Animal BehaviourAuthor(s): Andrew Sih, David L. Sinn, Gail L. PatricelliA major focus of research in behavioural ecology involves testing whether behaviour, on average, is adaptive. Here, we note that although studies often find that individuals differ in how well they perform adaptive behaviour (e.g. some individuals fit the predictions of optimal diet theory better than others, and some exhibit higher social skill than others), few studies have emphasized these consistent individual differences (CIDs) in behavioural skill. We define behavioural skill as performance in decision making on a particular task, while competence involves a collection of skills on a suite of related tasks. After discussing the definition of these and related terms, we present some examples and briefly describe how to quantify CIDs in skill and competence. We then present a three-level conceptual framework for organizing thinking on skill and competence. For the central level, behavioural skill per se, we note that for many ecologically important tasks (e.g. foraging, mating), success depends on decision making in three sequential steps: situation choice (e.g. patch choice that determines encounter rates with food items or potential mates), engagement choice (e.g. diet or mate choice) and execution choice (e.g. prey capture or courtship tactics). At a foundational level, we discuss three types of mechanisms that underlie behavioural skills: (1) genetic and neuroendocrine mechanisms; (2) development and learning (expertise); and (3) cognition. At a higher level, we outline understudied issues regarding suites of correlated skills both within a context (e.g. is skill in foraging patch choice correlated with skill in diet choice') and across contexts (e.g. is skill in diet choice correlated with skill in mate choice'), and we discuss reasons why different skills might be either positively or negatively correlated. We conclude with some remarks regarding evolutionary issues and ecological implications.

Abstract: Publication date: Available online 24 June 2019Source: Animal BehaviourAuthor(s): Elizabeth A. Hobson, Vanessa Ferdinand, Artemy Kolchinsky, Joshua GarlandExplaining how and why some species evolved to have more complex social structures than others has been a long-term goal for many researchers in animal behaviour because it would provide important insight into the links between evolution and ecology, sociality and cognition. However, despite long-standing interest, the evolution of social complexity is still poorly understood. This may be due in part to researchers focusing on the feasibility of quantifying aspects of sociality, rather than what features are characteristic of animal social complexity in the first place. Any given approach to studying complexity can tell us some things about animal sociality, but may miss others, so it is critical to decide first how to conceptualize complexity before jumping in to quantifying it. Here, we briefly summarize five existing approaches to measuring social complexity. Then, we highlight three fundamental concepts that are commonly used in the field of complex systems: (1) scales of organization, (2) compression and (3) emergence. All of these concepts are applicable to the study of animal social systems, but are not often explicitly addressed in existing social complexity measures. We discuss how these concepts can provide a rigorous foundation for conceptualizing social complexity, the potential benefits of incorporating them and how existing measures do (or do not) include them. Ultimately, researchers need to critically evaluate any measure of animal social complexity in order to balance the biological relevance of the aspect of sociality they are quantifying with the feasibility of obtaining enough data.

Abstract: Publication date: Available online 17 June 2019Source: Animal BehaviourAuthor(s): Trevor D. Price, Mary Caswell Stoddard, Steven K. Shevell, Natasha I. BlochThe past 20 years have seen a surge of interest in how animals perceive colour, setting the stage for a much more detailed examination of how colour perception differs among species, how a species’ colour perception relates to its environment and how it all fits into the framework of animal communication. We need to address two major questions: first, how do general mechanisms of signal processing work within whole clades of animals, and second, how do these mechanisms modulate differences among related species within clades' The receptor noise-limited (RNL) model (Vorobyev & Osorio, 1998) has made a critical advance in the field. Relevant parameters of the model, including screening pigments in the eye, visual pigments and relative numbers of the different receptor cells, can be measured to predict how species detect objects in their environment, based on wavelength. Details of the opponent channels, however, which compare the outputs of the retinal receptors and can determine the signals sent to the brain, are unknown for most species and are not required by the model. Here, we unpack the RNL model, focusing on experiments in humans and birds, and explore the impact of including specific opponent channels in the model. Incorporating opponent channels into the RNL model could help us better understand the selective forces and coevolutionary processes that shape the visual system and determine visual adaptations. Present evidence shows that the RNL model works as a good first approximation and points to critical parameters we need to measure, such as noise in receptor cells.

Abstract: Publication date: Available online 6 June 2019Source: Animal BehaviourAuthor(s): Todd M. Freeberg, Katherine E. Gentry, Kathryn E. Sieving, Jeffrey R. LucasSocial cognition involves a wide range of processes, including the ability to recognize group members, to remember past interactions with them and to influence their behaviour strategically. Key arguments and findings in studies of the evolution of social cognition revolve around individuals flexibly and adaptively influencing the behaviour of others. One of the most effective ways of influencing the behaviour of others is through communication. Curiously, however, research focused on the evolution of social cognition rarely addresses communication in the species being studied. Here we describe four major hypotheses to explain the evolution of social cognition and, for each, raise specific predictions regarding communication and how it relates to social cognition. We argue that because communication is foundational to social cognition, studies of communication should be a core feature of future work on the evolution of social cognition.